lee de foeest



PATENTED JAN. 12, 1904.

INVENTO/Y TTOHNEY L. DE FOREST. GENERATING SET .FOR WIRELESS TBLEGRAPHY.

APPLICATION FILED JUNE 17, 1903.

no MODEL Patented January 12, 1904.

PATENT OFFICE.

LEE DE FOREST, OF NEW YORK, N. Y.

GENERATING SET FOR WIRELESS TELEGRAPHY- SPECIFICATION forming part of Letters Patent No. 749,435, dated January 12, 1904.

Application filed June 1'7, 1903. Serial No. 161,889. (No model.)

To all whom it may concern: Be it known that 1, LEE DE FoREs'r, a citizen of the United States, and a resident of the city, county, and State of New York, have ini 5 vented certain new and useful Improvements in Generating Sets for Wireless Telegraphy, of which the following is a specification.

My invention relates to an improved form of transmitting apparatus for wireless teleg- 1o raphy, the same comprising a complete selfcontained set adapted to be used in all locations and to be readily movable from place to place. In smaller sizes it is especially adapted for use as a portable set to be moved at will from place to place. 1 The object of my invention is to produce a generating apparatusfor a transmitter of an improved and simple character and to combine the advantages-such as portability, simplicity, readiness, and adaptabilityto all situations, of an explosive-engine as a source of power, with the advantages of an alternatingcurrent generator as the primary source of electromotive force. The scope of my invention will be defined by the claims hereunto annexed.

The drawing accompanying herewith shows a transmitting set embodying my invention in a form now preferred by me. This drawing is of a diagrammatic character and is not intended to show the exact mechanical structure and arrangements of the parts, as these may be infinitely varied without the resulting mechanism being other than substantially in conformity with that herein shown.

It is often desirable or necessary to use wireless-telegraph transmitters in places and I under conditions under which the usual means for producing the required electromotive force such, for instance, as batteries or a supply of electricity or steamare not appli- H cable. This is especially true of sets which I are designed to be'portable and must therefore be kept light in weight and capable of operation anywhere. With these facts in view I have designed a transmitting set which is diagrammatically shown in the accompanying drawing.

In the drawing, D represents an explosiveengine, ordinarily one which uses a liquid hydrocarbon, although in some cases gas might be used. This engine is connected with and turns a generator G, which is preferably an alternating-current generator. It might at times be possible to directly connect the engine and generator; but questions of practicable or desirable speed would usually dictate a connection whereby the speed of the generator is increased. Such a connection, by means of a belt F running upon the fly-wheel of the engine and a pulley upon the generator, is shown. The potential of the generatorcurrent would ordinarily require to be raised before it is suitable for use at the spark-gap.

This I do by means of a static step-up transformer T. The primary of this transformer may be directly in the generator-circuit, or, as is herein shown, a unitary or choke transformer T may be interposed between the two. This choke-transformer is one in which there is neither a rise nor fall of potential, the purpose thereof not being to change the potential, but to provide a safeguard for the generator against the high potential used at the spark-' gap.

A key C is placed preferably in the low-potential circuit. The circuit containing the secondary of the step-up transformer T has the radiating antenna A and the ground E connected therewith and contains the sparkgap S. Preferably also this circuit contains choke-coils K K to prevent the high-frequency oscillations of the spark-gap from getting back into the transformer and puncturing the insulation. This circuit also, preferably, has condensers L in shunt about the spark-gap.

I prefer that the engine be of relatively large capacity, having a considerable reserve power over that required for turning the dynamo. I have found that a two-and-a-halfhorse-power engine, with a one-kilowatt generator and a speed-governor, gives good results in steadiness of running. With such a ratio between engine and generator no perceptible variation of speed is caused by opening or closing the switch. I prefer to use a primary current in the generator of five hundred volts, putting the key in this circuit,

and to step this up in the transformer to twenty thousand or twenty five thousand Volts. An apparatus of this type enables me to use an alternating current at all times, which I much prefer to do. Using a direct current necessitates the employment of inductioncoils and interrupters, which are fruitful sources of trouble. Moreover, batteries involve the necessity of being adjacent a primary source of electricity, from which they may be recharged, and hence are not independent of other and heavier apparatus.

With the apparatus herein described by me it is possible to use an unlimited amount of power. It is also the most compact, least costly, and most direct application of power for the purpose. It can be used in many places where storage batteries are unavailable. It saves space and weight and is not subject to such rapid deterioration. I have placed such sets upon boats, which may be done as well upon sailing vessels as up'on steamers.

The above form of apparatus is self-contained and may be placed anywhere and operated without reference to proximity to some source from which power may be had. The hydrocarbon required to run it is of very little weight and bulk and may be readily transported to any location. It may also be readily moved from place to place and is truly portable. For size and weight of part and supplies it is more powerful for a given weight than any other type of apparatus. It

is also simple in construction and operation and reliable in service.

What I claim, and desire to secure by Letters Patent, is

1. A. transmitting set for wireless telegraphy comprising an explosive-engine, a dynamo driven thereby, a unitary or choke transformer receiving the current from said dynamo, a step-up transformer receiving the current delivered by the choke-transformer, a sparking-circuit receiving the current delivered by the step-up transformer, and a radiating-conductor and earth connected with said sparking-circuit.

2. A transmitting set for wireless telegraphy comprising an explosive-engine, a dynamo driven thereby, a unitary or choke transformer receiving the. current from said dynamo, a step-up transformer receiving the current delivered by the choke-transformer, an oscillatory circuit containing the secondary of the step-up transformer and a sparkgap, an antenna and a ground connected with said oscillatory circuit, and means for controlling the energy to produce signals.

In testimony whereof have hereunto affixed my signature, this 10th day of June, 1903, in the presence of two witnesses.

LEE DE FOREST. 

